Synthetic approach to borrelidin fragments: focus on key intermediates

• Yudhi Dwi Kurniawan,
• Zetryana Puteri Tachrim,
• Teni Ernawati,
• Faris Hermawan,
• Ima Nurasiyah and
• Muhammad Alfin Sulmantara

Beilstein J. Org. Chem. 2025, 21, 1135–1160, doi:10.3762/bjoc.21.91

• , tert-butyl hydroperoxide (TBHP), and Ti(OiPr)4, resulting in the desired epoxide 63 with a 90% yield. Regioselective reductive opening of this epoxide was successfully carried out with Red-Al®, yielding diol 79. The more reactive primary alcohol in diol 79 was selectively masked as TBDPS ether 80 (94

Investigations of amination reactions on an antimalarial 1,2,4-triazolo[4,3-a]pyrazine scaffold

• Henry S. T. Smith,
• Ben Giuliani,
• Kanchana Wijesekera,
• Kah Yean Lum,
• Sandra Duffy,
• Aaron Lock,
• Jonathan M. White,
• Vicky M. Avery and
• Rohan A. Davis

Beilstein J. Org. Chem. 2025, 21, 1126–1134, doi:10.3762/bjoc.21.90

• ), 139.7 (C-9), 135.0 (C-13), 130.3 (C-6), 129.8 (2C, C-11, C-15), 129.4 (2C, C-12, C-14), 125.1 (C-10), 106.0 (C-5), 57.4 (C-18), 45.1 (2C, C-20, C-21), 37.9 (C-17); LRMS (ESI-SQ) m/z: 317 [M + H]+; HRESIMS–qTOF (m/z): [M + H]+ calcd for C15H1835ClN6, 317.1276; found, 317.1279. tert-Butyl(4-((3-(4

Recent advances in synthetic approaches for bioactive cinnamic acid derivatives

• Betty A. Kustiana,
• Galuh Widiyarti and
• Teni Ernawati

Beilstein J. Org. Chem. 2025, 21, 1031–1086, doi:10.3762/bjoc.21.85

• in situ nitro reduction using Mn powder to afford the amide intermediate 42. The acid halide once again was applied for cinnamic acid amidation. Xiao and co-workers (2021) performed a transesterification and aminolysis of the tert-butyl ester 43 simply by using PCl3 through in situ generation of the

• 89 from the corresponding dioxazolone 88 in excellent yields via reductive elimination from intermediate 90 (Scheme 26) [62]. Hu and co-workers (2019) also employed a Cu salt (Cu(OTf)2) to synthesize N-difluoroethylimide 91 from cinnamic acid (7) and tert-butyl nitrite (TBN) in good yield via

• . Similarly, Silvani and co-workers (2022) also reported a multicomponent Ugi-type reaction of cinnamic acid (7), aldehyde/ketone, (S)-β-phenyl β-aminoboronate 367, and tert-butyl isocyanide to give the corresponding pharmacophoric β-substituted β-amido boronates 368–370 in moderate yields (Scheme 80B) [136

Recent total synthesis of natural products leveraging a strategy of enamide cyclization

• Chun-Yu Mi,
• Jia-Yuan Zhai and
• Xiao-Ming Zhang

Beilstein J. Org. Chem. 2025, 21, 999–1009, doi:10.3762/bjoc.21.81

• attack of the electron-rich arene on the acyliminium ion occurs from the Si-face. This stereochemical outcome is attributed to the steric discrepancy of the phenyl or tert-butyl group and the hydroxy group. The resulting tricyclic products could be further elaborated by elimination or amide reduction to

• diastereo- and enantioselectivities. The substituent on the enamide could be varied from aryl to tert-butyl groups, though the terminating aryl group still necessitates an electron-rich arene. As was found in their previous work, the steric hindrance of the phenyl or tert-butyl group was supposed to be

Recent advances in controllable/divergent synthesis

• Jilei Cao,
• Leiyang Bai and
• Xuefeng Jiang

Beilstein J. Org. Chem. 2025, 21, 890–914, doi:10.3762/bjoc.21.73

• enantiocontrol. Conversely, the bulky tert-butyl-decorated (R)-spirophosphoramidite L5 imposed a confined cavity, steering selectivity toward Si–C(sp2)-bond activation and predominantly afforded the regioisomeric (S)-2-silacyclohexenylarenes 18. In 2025, Gong and co-workers reported a visible-light-mediated

• achieved selective synthesis of either enantiomer of a target product by controlling the reaction duration (Scheme 13) [42]. When performing the asymmetric intermolecular allylic amination of 6-hydroxyisoquinoline (49) with tert-butyl(1-phenylallyl)carbonate ((rac)-50) using an Ir catalyst derived from [Ir

Chitosan-supported CuI-catalyzed cascade reaction of 2-halobenzoic acids and amidines for the synthesis of quinazolinones

• Xuhong Zhao,
• Weishuang Li,
• Mengli Yang,
• Bojie Li,
• Yaoyao Zhang,
• Lizhen Huang and
• Lei Zhu

Beilstein J. Org. Chem. 2025, 21, 839–844, doi:10.3762/bjoc.21.67

• investigated the reactions of different 2-halobenzoic acid derivatives with amidines where R2 was a tert-butyl group. The results showed that 2-bromobenzoic acid derivatives (3j–k, 55−65% yields) displayed lower activity compared to 2-iodobenzoic acid derivatives (3i–l, 73−90% yields), with a decrease in

Recent advances in the electrochemical synthesis of organophosphorus compounds

• Babak Kaboudin,
• Milad Behroozi,
• Sepideh Sadighi and
• Fatemeh Asgharzadeh

Beilstein J. Org. Chem. 2025, 21, 770–797, doi:10.3762/bjoc.21.61

• the gram-scale preparation of some samples. An electrochemical flow system was used in this method, in which carbon and platinum electrodes were used as the anode and cathode, respectively, at a constant current of 55 mA (Scheme 8). Due to the steric hindrance caused by the tert-butyl group, the

Recent advances in allylation of chiral secondary alkylcopper species

• Minjae Kim,
• Gwanggyun Kim,
• Doyoon Kim,
• Jun Hee Lee and
• Seung Hwan Cho

Beilstein J. Org. Chem. 2025, 21, 639–658, doi:10.3762/bjoc.21.51

• transfer, X-ray crystallographic analysis of the (tert-butyl)(adamantyl)Bpin·Li(THF)2 complex revealed that the B–(adamantyl) bond is shorter than the B–(tert-butyl) bond (1.673 vs 1.692 Å). DFT calculations further illuminated the underlying mechanism by comparing two distinct transition states: TS1

• involving adamantyl transfer and TS2 involving tert-butyl transfer (Scheme 9). Analysis of these transition states revealed that both require significant pyramidalization of the transferring carbon center, with the barrier for adamantyl transfer (TS1) being 2.3 kcal/mol higher than that for tert-butyl

• transfer (TS2). The structural features of the tert-butyl group allow more efficient pyramidalization compared to the rigid adamantyl framework, suggesting that the flexibility of the transferring group plays a crucial role in facilitating transmetalation. Copper hydride chemistry for enantioselective

Total synthesis of (±)-simonsol C using dearomatization as key reaction under acidic conditions

• Xiao-Yang Bi,
• Xiao-Shuai Yang,
• Shan-Shan Chen,
• Jia-Jun Sui,
• Zhao-Nan Cai,
• Yong-Ming Chuan and
• Hong-Bo Qin

Beilstein J. Org. Chem. 2025, 21, 601–606, doi:10.3762/bjoc.21.47

• DIPEA, affording compound 17 with an 89% yield [11]. For the following alkylation step with tert-butyl bromoacetate, three bases were tested: potassium carbonate, cesium carbonate, and sodium hydride. Considering the targeted alkylation of a phenolic hydroxy group and the pKa requirements of this

Asymmetric synthesis of β-amino cyanoesters with contiguous tetrasubstituted carbon centers by halogen-bonding catalysis with chiral halonium salt

• Yasushi Yoshida,
• Maho Aono,
• Takashi Mino and
• Masami Sakamoto

Beilstein J. Org. Chem. 2025, 21, 547–555, doi:10.3762/bjoc.21.43

• reaction; the stereoselectivity of product 17j drastically dropped. The scope for the pre-nucleophile showed that phenyl-substituted 16b provided 17k in 94% yield with high diastereoselectivity, albeit with decreased enantioselectivities. Methyl ester 16c and tert-butyl ester 16d were also applied to the

Vinylogous functionalization of 4-alkylidene-5-aminopyrazoles with methyl trifluoropyruvates

• Judit Hostalet-Romero,
• Laura Carceller-Ferrer,
• Gonzalo Blay,
• Amparo Sanz-Marco,
• José R. Pedro and
• Carlos Vila

Beilstein J. Org. Chem. 2025, 21, 533–540, doi:10.3762/bjoc.21.41

• -aminopyrazole 2. Compounds 3ab and 3ad were obtained in a comparable yield (54 and 46%) from 1,3-dimethyl-1H-pyrazol-5-amine (2b) or 3-methyl-1-(p-tolyl)-1H-pyrazol-5-amine (2d). On the other hand, 1,3-diphenyl-1H-pyrazol-5-amine (2c) provided the corresponding product 3ac in much lower yield (16%). If a tert

• -butyl group is present in the C-3 position of the pyrazole as in the case of substrate 2e, the reaction did not take place, likely due to a considerable increase in steric hindrance. We also attempted to synthesize 4-(alkenyl)-5-aminopyrazoles using an acyclic ketone, such as acetone, but unfortunately

Cryptophycin unit B analogues

• Thomas Schachtsiek,
• Jona Voss,
• Maren Hamsen,
• Beate Neumann,
• Hans-Georg Stammler and
• Norbert Sewald

Beilstein J. Org. Chem. 2025, 21, 526–532, doi:10.3762/bjoc.21.40

• macrolactamisation [21]. The syntheses of required unit A [28], C [29][30], and D [31] building blocks were accomplished as described previously. tert-Butyl-protected leucic acid 14 and Fmoc-β-aminopivalic acid (15) were connected by Steglich esterification (Scheme 2) and after cleavage of the tert-butyl ester group

Synthesis of N-acetyl diazocine derivatives via cross-coupling reaction

• Thomas Brandt,
• Pascal Lentes,
• Jeremy Rudtke,
• Michael Hösgen,
• Christian Näther and
• Rainer Herges

Beilstein J. Org. Chem. 2025, 21, 490–499, doi:10.3762/bjoc.21.36

• except the preparation of the aminoaniline building block tert-butyl (2-amino-5-bromophenyl)carbamate (5), which was prepared by Boc-protection of the 5-bromo-2-nitroaniline (6) and subsequent reduction of the nitro group (see Supporting Information File 1, section II.1). Cross-coupling reactions Stille

• halogenated N-acetyl diazocines according to the procedure of Maier et al. [34] with tert-butyl carbamate resulted in the formation of Boc-protected amino-substituted N-acetyl diazocine 19 in a yield of 72%. However, the reaction only took place if iodo N-acetyl diazocine 3 was used as starting material

The effect of neighbouring group participation and possible long range remote group participation in O-glycosylation

• Rituparna Das and
• Balaram Mukhopadhyay

Beilstein J. Org. Chem. 2025, 21, 369–406, doi:10.3762/bjoc.21.27

Synthesis, structure, ionochromic and cytotoxic properties of new 2-(indolin-2-yl)-1,3-tropolones

• Yurii A. Sayapin,
• Eugeny A. Gusakov,
• Inna O. Tupaeva,
• Alexander D. Dubonosov,
• Igor V. Dorogan,
• Valery V. Tkachev,
• Anna S. Goncharova,
• Gennady V. Shilov,
• Natalia S. Kuznetsova,
• Svetlana Y. Filippova,
• Tatyana A. Krasnikova,
• Yanis A. Boumber,
• Alexey Y. Maksimov,
• Sergey M. Aldoshin and
• Vladimir I. Minkin

Beilstein J. Org. Chem. 2025, 21, 358–368, doi:10.3762/bjoc.21.26

• interaction of 2,3,3-trimethylindolenine with 3,5-di(tert-butyl)-1,2-benzoquinone leads to the formation of indolo[1,2-a]indoline derivatives [23], while the presence of a nitro group in 4,6-di(tert-butyl)-3-nitro-1,2-benzoquinone the reaction with 2,3,3-trimethylindolenine leads to an o-quinone ring

• reactions of 2-methylquinolines with 3,5-di-(tert-butyl)-1,2-benzoquinone [1] and benzophenones with o-chloranil [15]. The norcaradiene derivatives 5, formed in the next step by the intramolecular cyclization reaction of 4, undergo thermal isomerization into 2,3-dihydrotropolones 6. The formation of 2

Molecular diversity of the reactions of MBH carbonates of isatins and various nucleophiles

• Zi-Ying Xiao,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2025, 21, 286–295, doi:10.3762/bjoc.21.21

• yields. The single crystal structure of the compound 6e was determined by X-ray diffraction (Figure 3). The similar reaction of more nucleophilic tri(tert-butyl)phosphine and MBH carbonate of isatin resulted in a mixture of products. After carefully screening the reaction conditions, we found that DABCO

• successfully promoted reaction of tri(tert-butyl)phosphine and MBH carbonates of isatins in toluene at 80 °C for three hours. These conditions resulted in mixtures of conjugated triene cis/trans-isomers 7a–d and 8a–d with nearly 4:1 ratios (Table 2). It should be pointed out that similar conjugated trienes

Synthesis and characterizations of highly luminescent 5-isopropoxybenzo[rst]pentaphene

• Islam S. Marae,
• Jingyun Tan,
• Rengo Yoshioka,
• Zakaria Ziadi,
• Eugene Khaskin,
• Serhii Vasylevskyi,
• Ryota Kabe,
• Xiushang Xu and
• Akimitsu Narita

Beilstein J. Org. Chem. 2025, 21, 270–276, doi:10.3762/bjoc.21.19

• well-structured absorption peaks clearly showing the vibronic progressions. BPP-OiPr 3 also exhibited a small peak located at 442 nm with the molar extinction coefficient (ε) of 1800 M−1 cm−1, which was similar to the previous observations of the dark S1 states for BPP 2 and its mesityl- and tert-butyl

• -butyl-substituted BPP (BPP-t-Bu, PLQY: 0.47) (Figure 2b) [21][22]. Considering that two tert-butyl groups should more effectively hinder the aggregation than one isopropyl group, we tentatively attribute the enhanced PLQY of 3 to the reduced molecular symmetry, which can relax the selection rule and

• exhibited similar emission spectra in toluene with maxima at 436 and 443 nm, respectively, with well-defined vibronic structures (Figure 2b). Notably, the absolute PLQY of BPP-OiPr 3 was measured to be 0.73, demonstrating a remarkable enhancement of the photoluminescence from BPP 2 (PLQY: 0.13) and tert

Synthesis of disulfides and 3-sulfenylchromones from sodium sulfinates catalyzed by TBAI

• Zhenlei Zhang,
• Ying Wang,
• Xingxing Pan,
• Manqi Zhang,
• Wei Zhao,
• Meng Li and
• Hao Zhang

Beilstein J. Org. Chem. 2025, 21, 253–261, doi:10.3762/bjoc.21.17

• . For example, electron-donating groups (Me, tert-butyl, MeO, naphthyl) and electron-withdrawing groups (F, Cl, Br) attached to the benzene ring led to products 2a–i with yields ranging from 60% to 89%. Interestingly, products with strong electron-withdrawing substituents were obtained in moderate

• whether the reaction proceeded through a free radical mechanism, different free radical inhibitors were added to the reaction (reaction 7, Scheme 5). The addition of TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)oxyl) resulted in complete inhibition of the reaction, while BHT (2,6-di-tert-butyl-4-methylphenol

Nickel-catalyzed cross-coupling of 2-fluorobenzofurans with arylboronic acids via aromatic C–F bond activation

• Takeshi Fujita,
• Haruna Yabuki,
• Ryutaro Morioka,
• Kohei Fuchibe and
• Junji Ichikawa

Beilstein J. Org. Chem. 2025, 21, 146–154, doi:10.3762/bjoc.21.8

• -fluorobenzofuran (1a) when reacted with phenylboronic acid (2a) as well as arylboronic acids containing electron-donating groups, such as a methyl group at the 3-position (2b), two methyl groups at the 2- and 5-positions (2c), and a tert-butyl group at the 4-position (2d). The reaction with 3,5

• -dimethoxyphenylboronic acid (2e), which has electron-withdrawing groups on the aromatic ring, also yielded a satisfactory result of 73%. Additionally, using 2-fluoronaphtho[2,1-b]furan (1b), the reaction with phenylboronic acid (2a) and arylboronic acids with a methyl group at the 3-position (2b) or a tert-butyl group

Cu(OTf)₂-catalyzed multicomponent reactions

• Sara Colombo,
• Camilla Loro,
• Egle M. Beccalli,
• Gianluigi Broggini and
• Marta Papis

Beilstein J. Org. Chem. 2025, 21, 122–145, doi:10.3762/bjoc.21.7

• -difunctionalization of alkenes carried out with carbazates (N-aminocarbamates) and (hetero)arene nucleophiles or amines exploiting N-(tert-butyl)-N-fluoro-3,5-bis(trifluoromethyl)benzenesulfonamide (NFBS) as intermolecular hydrogen-atom-transfer reagent results in alkylarylation processes (Scheme 5) [19]. The

Recent advances in organocatalytic atroposelective reactions

• Henrich Szabados and
• Radovan Šebesta

Beilstein J. Org. Chem. 2025, 21, 55–121, doi:10.3762/bjoc.21.6

• and di-tert-butyl azodicarboxylate (Scheme 22) [45]. An added benefit to these products is that they possess an intramolecular hydrogen bond acting as a stabilizing factor and products 68 were prepared in good to very good yields and excellent enantiomeric purities. Based on the authors’ design

Synthesis, structure and π-expansion of tris(4,5-dehydro-2,3:6,7-dibenzotropone)

• Yongming Xiong,
• Xue Lin Ma,
• Shilong Su and
• Qian Miao

Beilstein J. Org. Chem. 2025, 21, 1–7, doi:10.3762/bjoc.21.1

• that the alkoxy groups in compound 10, which are positioned para or ortho to the reacting site, play an important role in the Scholl reaction to form compound 3. Similar substrates, where the alkoxy groups are replaced by hydrogen atoms or a 4-tert-butyl group, did not yield product 3 under similar

Synthesis, characterization, and photophysical properties of novel 9‑phenyl-9-phosphafluorene oxide derivatives

• Shuxian Qiu,
• Duan Dong,
• Jiahui Li,
• Huiting Wen,
• Jinpeng Li,
• Yu Yang,
• Shengxian Zhai and
• Xingyuan Gao

Beilstein J. Org. Chem. 2024, 20, 3299–3305, doi:10.3762/bjoc.20.274

• hand, we turned our attention to the synthesis of PhFlOP-based compounds through a Cs2CO3-facilitated nucleophilic substitution with substituted carbazoles as the nucleophiles (Scheme 2). For example, tert-butyl, bromo, carbazolyl, or phenyl substituents were introduced into the carbazoles. To our

Reactivity of hypervalent iodine(III) reagents bearing a benzylamine with sulfenate salts

• Beatriz Dedeiras,
• Catarina S. Caldeira,
• José C. Cunha,
• Clara S. B. Gomes and
• M. Manuel B. Marques

Beilstein J. Org. Chem. 2024, 20, 3281–3289, doi:10.3762/bjoc.20.272

• salts [34]. Under these conditions, N-benzyl-4-methylbenzenesulfinamide (6aa) was not observed, and N-benzyl-p-toluenesulfonamide (5aa) was isolated in 29% yield (Table 1, entry 4). To prevent the regeneration of tert-butyl 3-(p-tolylsulfinyl)propanoate (4a) and employ milder conditions, a study was

• is more favorable at higher temperatures [4]. Due to the reversibility of the retro-Michael addition, an experiment was carried out using an excess of tert-butyl 3-(p-tolylsulfinyl)propanoate (4a) leading to an increase in the yield of the corresponding sulfonamide 5aa by 38% (Table 1, entry 6). A

• electrophilic amination reaction afforded sulfonamides 5aa, 5ba, 5da, and 5ea with moderate yields. However, no amination product was detected with tert-butyl 3-(benzylsulfinyl)propanoate (4c). This result suggests that aliphatic β-sulfinyl esters may not possess sufficient nucleophilicity to react with the

Synthesis of 2H-azirine-2,2-dicarboxylic acids and their derivatives

• Anastasiya V. Agafonova,
• Mikhail S. Novikov and
• Alexander F. Khlebnikov

Beilstein J. Org. Chem. 2024, 20, 3191–3197, doi:10.3762/bjoc.20.264

• isoxazole ring, both with electron-donating and electron-withdrawing groups, and the tert-butyl-substituted isoxazole 1j, we proceeded to obtain dicarboxylic acids 6 (Scheme 2). The isomerization of isoxazoles 1 into diacyl chlorides 2 was achieved by applying the conditions for the isomerization of 3-aryl

• not isomerize at room temperature, which is typical for highly sterically congested isoxazoles containing a 3-tert-butyl substituent [26]. The mechanism of such isomerizations of isoxazoles has been previously discussed using DFT calculations [25][26], which revealed the formation of an isoxazole–Fe

• isomerization to 3-aryl-2H-azirine-2,2-dicarbonyl dichlorides followed by their fast reaction at the same temperature with O- and N-nucleophiles. 3-Aryl-2H-azirine-2,2-dicarboxylic acids were prepared in 64–98% yield, whereas 3-(tert-butyl)-2H-azirine-2,2-dicarboxylic acid could not be obtained by this method